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1.
Summary The influence of pre-steaming on the drying rate, wood anatomy and shrinkage of regrowth Eucalyptus pilularis (blackbutt) was determined. Pre-steaming increased the drying rate by 7–16%. This resulted from a mobilisation and partial removal of heartwood extractives, probably allowing greater access of water molecules to cell walls, and therefore increased radial and tangential diffusion. Longitudinal permeability is unlikely to be significantly increased by pre-steaming, as tyloses appeared unaltered. Volumetric shrinkage was unchanged.The authors wish to thank K. W. Groves of the Department of Forestry, Australian National University for his comments, J. F. Marchant and R. Colley for technical assistance, and P. Lind for some of the statistical analyses. The New South Wales Timber Advisory Council Ltd provided financial support. The work reported in this paper formed part of a post-graduate research programme undertaken by the senior author at the Department of Forestry, Australian National University 相似文献
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The economic yield of chickpea, lentil, wheat, cauliflower, barseem, and toria in a 12-m-wide strip to the south of 8 ± 1-year-old Eucalyptus tereticornis shelterbelts (three different locations) was reduced by more than half. Among all the crops under study, the yield of chickpea was reduced by the maximum extent. The content of soil phytotoxins was maximum in the litter-free top soil surface, compared to that at 30 or 60 cm depths, at all distances from the Eucalyptus. Maximum content of phytotoxins was found at 1 m from the tree line for all depths. These soil phytotoxins impaired the germination of Lens esculentum, thus indicating an allelopathic effect. It is included that the poor perfornce of crops in the sheltered area is related to an allelopathic effect of the Eucalyptus. 相似文献
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Eucalyptus pilularis planted at three initial stocking densities of 833, 1111 and 1,667 stems ha?1 grown at either square or rectangular spacing was assessed for the effects of stocking and rectangularity on wood properties. Sample trees from each stocking and rectangularity combination were harvested at age 7 years and assessed for the commercially important wood properties of bow, as an indication of growth strain, shrinkage and basic density. Crown length ratio was used as an indicator of stand vigour and clear wood availability. Furthermore comment is made on the financial ramifications of wide inter-row spacing. Stocking and rectangularity significantly influenced bow but not shrinkage or basic density. Reducing within-row spacing to 2 m with a larger between-row-space of 6 m had minimal affect on wood properties. Reducing the number of rows, whilst still retaining a commercial stocking, reduces the establishment costs and increases the ease of mechanical harvesting without adversely affecting log value. 相似文献
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We studied the variability in longitudinal growth strains and wood basic density in five-year old trees from five clones (one tree per clone) of Eucalyptus tereticornis. Mean longitudinal growth strain in clones ranged from 466 to 876 μm. There was a significant difference between clones in growth strains and wood basic density. Clone 10 exhibited maximum growth strains and basic density, whereas clone 3 and clone 7 exhibited minimum growth strains and basic density, respectively. Within a tree, the growth strain variation with tree height was high but statistically insignificant while within tree variation in basic density was very small. There was no specific trend in variation in either strain or density within a tree. There was 5% 200% difference in growth strain on opposite sides of the logs. However two strains showed a strong positive correlation. There was a moderate positive association of wood basic density and mean growth strains in logs. The variation around the periphery emphasize the need to measure strain more than one, preferably on opposite sides at the same height, on a tree to know the mean strain level for the purpose of selection of clones. 相似文献
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T. C. Innes 《Wood Science and Technology》1996,30(6):373-383
Summary Tangential shrinkage was measured on longitudinal-tangential slices of separate earlywood and latewood from one board of Eucalyptus regnans F.Muell. at various temperatures. Large amounts of collapse shrinkage were measured in the latewood slices, and lesser amounts in the earlywood slices. Collapse shrinkage in the earlywood was found only when the slices were dried at temperatures above a minimum temperature (the collapse threshold temperature). End-coated board sections approximately 200 mm long were rapidly dried at dry-bulb temperatures below the collapse threshold temperature for earlywood. Incipient internal checks were found in the latewood of these boards. Board sections dried at higher temperatures showed internal checks starting in both early and latewood. A non-linear drying simulation model was modified to take the heterogeneous nature of wood into account. This model predicted that internal checks would form in this wood even if it were dried sufficiently slowly to avoid surface checking.Symbols D
Diffusion coefficient
- ec
Creep strain
- ei
Instantaneous strain
- em
Mechano-sorptive strain
- en
Net strain
- eu
Unconfined shrinkage strain
- EW
Earlywood
- FSP
Fibre saturation point
- LW
Latewood
- L-T
Longitudinal-tangential slice
- MC
Moisture content (kg water/kg dry wood)
- q
Moisture concentration
- R-T
Radial-tangential slice
- t
Time
- y
Depth in board
The author is pleased to acknowledge the assistance of Emeritus Professor A. R. Oliver, Associate Professor P. E. Doe, University of Tasmania, and the Australian Furniture Research and Development Institute 相似文献
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S. C. Chafe 《Wood Science and Technology》1986,20(3):253-262
Summary Examination of segmented increment cores from three trees of Eucalyptus regnans demonstrated radial variability as follows: collapse increased with distance from the periphery to about 85% of the radius where it commenced a precipitous decline towards the pith; total volumetric shrinkage increased to about 45% of the radius, gradually declined to 85% radius, then abruptly fell as with collapse; moisture content increased to about 75% radius and abruptly declined at 85–90%; basic density declined with distance from the periphery to about 75% radius, then showed a slight increase towards the pith; per cent saturation remained relatively constant from the periphery to about 90% of the radius, then abruptly declined. It is argued that compression failures in the fibre walls of the brittle heart core were responsible for the precipitous decline in collapse, moisture content and per cent saturation near the pith. Examination of data after separation by density into latewood and earlywood increments demonstrated that latewood tends to be more highly water saturated than earlywood. Similar levels of collapse for material of different densities and correspondingly different saturation values indicated that level of saturation was a more important determinant of collapse susceptibility in latewood than in earlywood. 相似文献
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Consistent germination of Eucalyptus sieberi L. Johnson seeds required a low vapor pressure deficit (< 5 x 10(-6) MPa) and a high matric water potential (> -5 x 10(-3) MPa). Eucalyptus sieberi seeds, under moist but less favorable conditions, were unable to germinate but underwent changes that enabled them to germinate more rapidly when suitable conditions occurred. Such pregerminative development was interrupted but not reversed by a dry period as long as eight months. This may explain how seeds of this species germinate successfully on the surface of exposed seedbeds subject to intermittent drying. 相似文献
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R. V. Rao S. Shashikala P. Sreevani V. Kothiyal C. R. Sarma P. Lal 《Wood Science and Technology》2002,36(3):271-285
Within tree variation in anatomical properties of four and half year old grown Eucalyptus tereticornis Sm. clones have been investigated and correlated with specific gravity. Vessel frequency, vessel diameter and fiber length
were found to vary significantly from bottom to top with no definite trend. Significant variation exists in all the clones
of different parameters. Fiber length was positively correlated with fiber diameter and double wall thickness. Tissue proportions
did not show any significant variation from bottom to top. However, highly significant differences have been found between
clones among four cell types except fibers. Specific gravity is positively correlated with ray percentage, fiber percentage
– vessel percentage ratio and negatively correlated with vessel percentage, while all other anatomical parameters including
height and girth have no effect.
Received 25 August 1998 相似文献
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S. C. Chafe 《Wood Science and Technology》1985,19(4):329-345
Summary The relationships among collapse, volumetric shrinkage, moisture content and basic density and their distribution within the stem were examined for trees of E. regnans. It was found that collapse and volumetric shrinkage each were significantly related to moisture content (positively), basic density (negatively), and (positively) to the derived values P (per cent of theoretical saturation) and Q (per cent of cell cavity volume containing water). Notwithstanding the inverse association evident between moisture content and density in the living tree, moisture content was shown to be independently related to each of collapse and volumetric shrinkage.Within the stem, collapse and volumetric shrinkage were negatively correlated with height in the tree although the significance of this relationship was qualified by the adjustment for other variables. Samples containing sapwood displayed collapse values significantly lower than heartwood samples. This was reflected in the presence of a positive relationship between collapse and distance from the periphery when all material was considered, but a negative relationship when sapwood-containing samples were omitted. Basic density was positively correlated with height in the tree and negatively correlated with distance from the periphery. Moisture content, P and Q were negatively correlated with both height in the tree and distance from the periphery although the latter relationship for moisture content was dependent on adjustment for density.The highly significant relationship between volumetric shrinkage and collapse suggested that the former could confidently be used in assessing collapse severity. Moisture content was determined to be an independent indirect indicator of collapse whereas basic density, P, Q and green density could all be of indicatory value, especially the last in view of its ease of measurement. 相似文献
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Bruno Clair Jérôme Alteyrac Arthur Gronvold Jaime Espejo Bernard Chanson Tancrède Alméras 《Annals of Forest Science》2013,70(8):801-811
Context
Tree orientation is controlled by asymmetric mechanical stresses set during wood maturation. The magnitude of maturation stress differs between longitudinal and tangential directions, and between normal and tension woods.Aims
We aimed at evaluating patterns of maturation stress on eucalypt plantation trees and their relation with growth, with a focus on tangential stress evaluation.Methods
Released maturation strains along longitudinal and tangential directions were measured around the circumference of 29 Eucalyptus nitens trees, including both straight and leaning trees.Results
Most trees produced asymmetric patterns of longitudinal maturation strain, but more than half of the maturation strain variability occurred between trees. Many trees produced high longitudinal tensile stress all around their circumference. High longitudinal tensile stress was not systematically associated with the presence of gelatinous layer. The average magnitude of released longitudinal maturation strain was found negatively correlated to the growth rate. A methodology is proposed to ensure reliable evaluation of released maturation strain in both longitudinal and tangential directions. Tangential strain evaluated with this method was lower than previously reported.Conclusion
The stress was always tensile along the longitudinal direction and compressive along the tangential direction, and their respective magnitude was positively correlated. This correlation does not result from a Poisson effect but may be related to the mechanism of maturation stress generation. 相似文献12.
施肥对桉树幼林生长量的影响 总被引:5,自引:0,他引:5
通过正交试验设计探索施用不同种类肥料、不同施肥方法对不同家系桉树幼林生长量的影响差异,结果表明:在福建省闽南海拔700 m以下丘陵山地以尾细桉M1(A3)+0.3 kg.株-1(分2次施)磷酸二铵(B1)+开放射沟施的方法(C3)最好,1 a高生长量达7.3 m、胸径达4.2 cm。 相似文献
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S. C. Chafe 《Wood Science and Technology》1990,24(4):311-326
Summary Brief presteaming of green, increment-core segments of mountain ash (E. regnans F. Muell) produced small but significant changes in a number of moisture-shrinkage parameters. Both total volumetric shrinkage and recoverable collapse were significantly greater in presteamed samples, the increase in collapse being largely attributable to an increase in moisture content after reconditioning (Mr). The change in shrinkage after reconditioning also was significantly related to changes in Mr. The change in Mr was interpreted as reflecting altered permeability in presteamed material and was shown to be negatively related to estimated residual collapse. Initial moisture content and per cent saturation showed a highly significant decrease after presteaming, while green volume showed a small but significant increase. Neither the estimated intersection point, unit shrinkage nor the R-ratio were significantly different after presteaming. However, the unit shrinkage-specific gravity relationship was changed by presteaming such that it more closely complied with Stamm's approximation.The author expresses his appreciation to Dr. Alan Miller for assistance with statistical analysis and to Mr. Chris McEvoy for technical assistance 相似文献
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《Forest Ecology and Management》1987,18(3):205-217
This paper presents a comparison of two common techniques used to improve seedling survival on hot, dry reforestation. Adjacent shelterwood and clearcut sites were located and instrumented to compare temperature and moisture environments. In addition, cardboard shadecards were placed beside half of the seedlings studied so that effects of this treatment could be assessed. Seasonal measurements or observations of soil moisture, soil temperature, solar radiation, air temperature, stomatal diffusion resistance, seedling phenology and survival provided the basis for comparisons. Shelterwoods and shadecards improved seedling survival in relation to the clearcut. Both treatments affected soil temperature but the nature of the effects was different. The shelterwood canopy decreased solar radiation incident at the soil surface and caused cooler soil temperatures throughout the soil profile. Shadecards reduced soil temperatures only to a depth of 20 mm. Both treatments reduced the duration of periods of high soil temperature.The shelterwood treatment delayed seasonal water loss and decreased seedling water stress as measured by stomatal resistance. Shadecards did not significantly affect seedling stomatal resistance. The differences in seedling survival caused by shadecards and shelterwoods are apparently due to different influences on the seedling microclimate. The shelterwood causes a large reduction in soil temperature as well as decreased seedling water stress. Shadecards modify the soil temperature environment less extensively and so have less effect on seedling survival. 相似文献
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Variation in density and moisture content of wood and bark among twenty Eucalyptus grandis progenies
Summary Variation in density and moisture content of Eucalyptus grandis wood and bark is described utilizing the trees established for a half-sib progeny test in southern Florida. Differences in density and moisture content among progenies were significant. Variations in wood properties were largely due to the genetic differences. No relationship was found between wood density and wood moisture content. Implications for genetic manipulation of wood quality for this species were discussed. 相似文献
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The effects of light, moderate and heavy branch pruning or lopping treatments (resulting in removal of 28-31, 56-60 and 80-82% of the foliage, respectively, unlopped control = 0%) were studied in 3-year-old black alder (Alnus glutinosa L. Gaertn.) plants. Within 24 h of lopping, transpiration rates decreased and water potentials increased. The effects of lopping continued for 48 days. The improved water status of the lopped plants enhanced water-use efficiency during the first 30 days. Regrowth was related to a combination of enhanced net assimilation rates during the first 30 days after lopping, use of current photoassimilates and stored carbohydrates in the roots (particularly in medium and heavily lopped plants) for the production of new leaf area, and delayed leaf senescence. The lightly and moderately lopped plants developed 62 and 57% more leaf area, respectively, than the unlopped plants, but total leaf area development was slower in the heavily lopped plants. Lightly lopped plants produced total biomass equivalent to that of unlopped plants, but the moderately and heavily lopped plants produced less biomass than the unlopped plants. During the first 30 days after lopping, there was a net loss of nodule dry matter and recovery to control values did not occur during the period of study. Immediately (24 h) after lopping, more (14)C-photosynthate was translocated to the roots of lopped plants than to the roots of unlopped plants. When a branch near the base of the main stem was fed (14)CO(2), (14)C-photosynthate translocation to the shoot increased with increasing intensity of lopping, at 50 days after lopping. 相似文献
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Resquin Fernando Navarro-Cerrillo Rafael M. Carrasco-Letelier Leónidas Rachid-Casnati Cecilia 《New Forests》2020,51(4):631-655
New Forests - According to some studies, the use of forest biomass for the generation of electric power and/or heat would result in a significant reduction in the emission of greenhouse gases. This... 相似文献
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